#Does cement absorb water how to#
#Does cement absorb water full#

Then it needs to stay moist for a minimum of 3 days to obtain its minimum acceptable strength. Click HERE for a video on the difference between evaporation set and chemical set compounds.Ĭoncrete needs a very specific water content for a few hours until it 'sets' - which means that it gets hard enough that more water or rain will not wash it away. If you re-wet plaster it remains hard because the chemical bonds are still there - as with concrete. (If you tried to 'pre-mix' them, they would simply harden in the bucket.) Both end up dry but if you re-wet the premixed compound, it gets soft again.

Premixed drywall compound (the stuff you buy wet in a bucket) must dry to get hard and power mixed drywall compounds and plasters use water for a chemical reaction - they get hard or cure first, then slowly dry out.

You may already have experience with this distinction between drying and curing with drywall compounds. Note that I did not say 'dry', but 'cure'. Different concrete mixtures, intended for different applications will each have their own proper 'slump' measurement.Ĭontrary to Mike's statement, water is not drawn in to become part of the concrete it is just the key element in permitting the chemical reactions to happen - what we call curing. Either too much or too little water will show up clearly with this test.

#Does cement absorb water full#

So the right quantity of water in concrete is measured by something called 'slump', packing the wet concrete into a little 'sand bucket' (not just any bucket but one made for this test), tipping it over like when making sand castles on the beach and measuring how much it slumps down from the full bucket size. If there is too little water, or you allow the water to evaporate too quickly, the chemical cure will not be complete and the concrete will end up weaker as well.

#Does cement absorb water how to#

This is also why you should really follow to the letter the package instructions when mixing your own concrete - unless you know how to do a 'slump' test. If there is too much water in the mixture, the chemicals and granules are thinned out and the resulting concrete will be weak - which is why water should never be added to specifically formulated pre-mixed concrete from a truck in order to make it flow - but rather special chemicals can be added called plasticizers that will make it flow more easily into its forms without reducing its final strength. The presence of water in a concrete mixture is essential to provide the environment in which the chemical reactions that cure concrete to a permanently hard substance can take place. So just what is the role of water while making concrete and after it is cured?

No, water does not become part of the concrete and it will eventually reach equilibrium with the environment around it, either getting wet or drying out. Yes as Mike says you can cover concrete with plastic and it will setup very well, in fact that is often done to help it set-up in dry weather. People are often a bit confused about things like this and half truths can cause a lot of household damage so let me share a bit of information about concrete so that we can all understand about water and concrete.

You could seal it with watertight plastic and the concrete will still setup exactly the same.' -Mike ( Self Leveling Concrete) This is a common misconception about concrete, in fact the water does not leave, it becomes part of the concrete. 'I notice in your section on self leveling concrete that you mention about needing to let the water out before putting anything on top of the new compound.